Substrate positioning for deposition machine

ABSTRACT

A deposition device is described. The deposition device has a substrate support and an imaging system disposed to image a portion of a substrate positioned on the substrate support. The imaging system comprises an LED light source and an imaging unit, and is coupled to a deposition assembly disposed across the substrate support.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication No. 63/198,555, filed Oct. 27, 2021 and is incorporated byreference in its entirety.

FIELD

Embodiments of the present invention generally relate to depositiondevices. Specifically, deposition devices having an attached but movableservice platform are described.

BACKGROUND

Deposition by Inkjet deposition is common, both in office and homeprinters and in industrial scale printers used for fabricating displays,deposition of large scale written materials, adding material tomanufactured articles such as printed circuit boards, and constructingbiological articles such as tissues. Most commercial and industrialinkjet deposition machines, and some consumer printers, use dispensersto apply material to a substrate. The dispenser ejects a controlledquantity of deposition material toward a substrate at a controlled timeand rate so that the deposition material arrives at the substrate in atarget location and makes a mark having a desired size and shape.

In some cases, such as in the display fabrication industries, very highprecision deposition is achieved by depositing very small volumes ofmaterial at very precise locations. The volumes may have dimension of 10μm in some cases and may be deposited in an area of dimension 15 μm. Toachieve such precision in placement of materials on a substrate, thesubstrate must be positioned precisely and/or the position of thesubstrate must be known precisely. Vision systems using cameras areroutinely used to photograph a substrate and determine its positionprecisely, but capturing the images and processing the images is timeconsuming. There is a need for a better way to precisely determine theposition of a substrate for inkjet printing.

SUMMARY

Embodiments described herein provide a deposition device, comprising asubstrate support; and a deposition assembly comprising an imagingsystem disposed across the substrate support, the imaging systemcomprising an LED light source.

Other embodiments described herein provide a method of imaging a featureon a substrate, comprising scanning the substrate relative to an imagingsystem comprising an LED light source and an imaging unit; activatingthe imaging unit before an extremity of the feature reaches anillumination field of the LED light source; activating the LED lightsource when a portion of the feature reaches the illumination field;deactivating the LED light source after an active time; and deactivatingthe imaging unit after an imaging time, wherein the imaging timeencompasses the active time.

Other embodiments described herein provide a deposition device,comprising a substrate support; and a deposition assembly comprising animaging system disposed across the substrate support, the imaging systemcomprising an LED light source fiber coupled to an optical assembly todirect radiation from the LED light source toward the substrate support;and an imaging unit disposed to capture radiation reflected through theoptical assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlyexemplary embodiments and are therefore not to be considered limiting ofits scope, may admit to other equally effective embodiments.

FIG. 1 is an isometric top view of a deposition device according to oneembodiment.

FIG. 2 is a block diagram of a position acquisition system according toone embodiment.

FIG. 3 is an algorithm diagram of a droplet ejection algorithm accordingto one embodiment.

FIG. 4 is a flow diagram of a method according to one embodiment.

FIG. 5 is a flow diagram summarizing a method that can be used with theapparatus and other methods described herein.

FIG. 6 is an isometric top view of a deposition device according toanother embodiment.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements and features of oneembodiment may be beneficially incorporated in other embodiments withoutfurther recitation.

DETAILED DESCRIPTION

A deposition device is described herein with a service platform that canbe deployed above the work surface of the deposition device and stowedadjacent to an end of the work surface at an elevation at leastpartially below a basis elevation of the work surface to allow forsubstrate loading and unloading. FIG. 1 is an isometric top view of adeposition device 100 according to one embodiment. The deposition devicehas a substrate support 102, a deposition assembly 104, and a holderassembly 106 for manipulating a substrate for deposition. The depositiondevice 100 includes a base 108, which is typically a massive object tominimize vibratory transmissions to the operative parts of thedeposition device 100. In one example, the base 108 is a granite block.The deposition assembly 104 includes a deposition assembly support 116comprising a stand 120 on each side of the base 108 and a rail or beam117 extending between the stands 120 across the substrate support 102.

The substrate support 102 has a first section 102A, a second section1028, and a third section 102C between the first and second section 102Aand 1028. The first and second sections 102A and 102B are staging areasfor substrates entering and leaving the deposition device 100, while thethird section 102C is a work section for positioning the substrate forprocessing relative to the deposition assembly support 116. Thesubstrate support 102 has a work surface 110 along with means for makingthe work surface 110 substantially frictionless. Here, the work surface110 is a gas cushion table that provides a gas cushion, for example air,oxygen depleted air, dry air, nitrogen, or other suitable gas on whichthe substrate floats. The work surface 110 features a plurality of holes(not shown) that allow jets of gas to exit, thus providing an upwardforce to maintain a substrate at a desired elevation above the worksurface 110. Some of the holes may also allow controlled withdrawal ofgas from the gas cushion floating the substrate support to provideprecise local control of substrate elevation. In one embodiment, thethird section 102C has gas providing holes and gas withdrawing holes.The gas providing and withdrawing holes provide independent control ofgas in the gas cushion and therefore substrate float height above thesubstrate work surface 110.

The deposition assembly 104 comprises a dispenser assembly 114 coupledto the beam 117. The dispenser assembly 114 includes a dispenser housing119 coupled to a deposition carriage 122 that rides along the beam 117to position the dispenser assembly 114 in relation to a substratedisposed on the third section 102C of the substrate support 102. Thedispenser housing 119 contains one or more dispensers (not shown) thateject volumes of deposition material onto a substrate positioned on thesubstrate support 102 under the deposition assembly 104.

In operation, a substrate is positioned under the deposition assembly104 by the holder assembly 106. The holder assembly 106 acquires securecontact with the substrate upon loading and moves the substrate alongthe substrate support 102 to position the substrate with respect to thedeposition assembly 104 for dispensing print material onto the substratein a precise fashion. The holder assembly 106, in this case, generallyextends along the substrate support 102 in a first direction totranslate the substrate in the first direction during deposition. Thefirst direction is denoted in FIG. 1 by arrow 124. The dispenserassembly 114 generally moves in a second direction substantiallyperpendicular to the first direction, as defined by the beam 117, whichextends substantially in the second direction, denoted in FIG. 1 byarrow 126. The second direction 126 is sometimes referred to as the “xdirection,” and the beam 117 as the “x beam.”

A controller 132 is operatively coupled to the holder assembly 106 andthe deposition assembly 104 to control movement of, and deposition onto,a substrate positioned on the substrate support. The controller 132 maydirectly control actuators of the holder assembly 106 and the depositionassembly 104, or the controller 132 may be operatively coupled to aholder assembly controller coupled to the holder assembly 106 and to adeposition assembly controller coupled to the deposition assembly 104.The controller 132 controls movement and positioning of the substrate,if any, on the substrate support 102. The controller 132 also controlsmovement of the dispenser assembly 114 along the beam 117 and ejectionof deposition material from the dispenser assembly 114 onto thesubstrate.

An imaging system 150 is coupled to the dispenser assembly 114. Theimaging system 150 includes an LED light source 152 and an imaging unit154. The LED light source 152 directs radiation toward a substratepositioned on the substrate support 102 positioned under the dispenserassembly 114. The imaging unit 154 detects illuminating radiationreflected from the substrate. The imaging unit 154 can include a digitalcamera or other high precision imaging capture component. The imagingunit also include optics for focusing the radiation into the imagecapture component. The LED light source 152 and imaging unit arearranged such that the LED light source 152 provides an illuminationfield on the substrate that is within the imaging field of the imagingunit 154.

The LED light source 152 may emit radiation that is selected to minimizeimpacts on other aspects of the deposition device 100 and the processesperformed by the deposition device 100. For example, in many cases,curable materials are deposited on a substrate using the depositiondevice 100. Such materials are routinely curable using short-wavelengthelectromagnetic radiation, such as ultraviolet radiation. Thesematerials are also, frequency, sensitive to short-wavelength visibleradiation, and can have minor sensitivity to longer-wavelength visibleradiation. Because uniform processing can be important to achieving thehigh precision results in industries such as the display fabricationindustry, the LED light source can be selected to emit long wavelengthradiation to minimize any impact on deposition materials. Light sourceshaving emission wavelengths of 650 nm or more are useful in this regard.In one example, the light source has emission wavelength of 650 nm. Inanother example the light source has emission wavelength of 800 nm.

The LED source can be an array of LEDs selected to provide a desiredillumination field that enables the imaging system to capture an imagein a very short time. Imaging in a very short time enables capturingclear images of an area of a moving substrate. The combination of lightsource and image capture component can also be selected to maximizesensitivity of the image capture component to the radiation emitted bythe LED light source. For example, a Dalsa Nano M2020 camera hasnear-peak sensitivity at a wavelength of 650 nm. Silicon-based NIR imagecapture units typically have peak sensitivity around 800 nm. LED lightsources can be used that have emission spectra that peak at or nearthese wavelengths.

The LED light source 152 can be fiber coupled to translate the LED lightemission to an emission plane that can be located close to thesubstrate. Use of LED light sources provides high luminosity and fasttransition to and from peak luminosity without the need to decorrelatelaser light. For many display applications, a substrate has apositioning feature, such as a fiducial mark, that can be used toprecisely calibrate the position of the substrate. The mark may besmall, for example 0.5-5 mm in dimension. In some cases, the mark has across-shape. The fiber coupling allows the radiation emission plane tobe positioned such that the radiation produces a uniformly bright spotthat encompasses all, or a substantial part of, the view field needed toascertain the position of a mark.

The imaging system 150 is configured to capture an image while thesubstrate and the dispenser assembly 114 move relative to one another.The relative movement can be as fast 1 m/sec in some cases. An imagingcontroller 158 is operatively coupled to the LED light source 152 andthe image capture unit 154 to drive image capture while relativemovement is underway. Here, the LED light source has a pulse capabilityat least as short as a few μsec, meaning that the average intensity ofthe emitted radiation field increases, reaching half its maximum valueat a pulse start time, and decreases, reaching half its maximum value ata pulse end time, in a pulse duration, defined as the duration from thepulse start time to the pulse end time, of a few μsec, or even less than1 μsec in some cases. The imaging controller 158 is realized in aprinted circuit board containing the digital circuitry that communicatesinstructions to the image capture unit 154 to start and stop imagecapture and to a power source or a switch electrically coupled betweenthe power source and the LED light source 152 to switch on and switchoff, or alternately to emit a pulse having a defined duration. Theimaging controller 158 is operatively coupled to the controller 132, andoptionally to other controllers such as holder assembly controllers anddispenser assembly controllers, to send and receive signals representinginformation used to control imaging of the substrate. The imagingcontroller 158 is configured to send signals representing imagescaptured by the imaging capture unit 154 to the controller 132 foranalysis. The imaging controller 158 is also configured to control theimage capture unit 154 and the LED light source 152 to capture an imagewhen a feature of the substrate, such as positioning feature, isexpected to be within the field of view of the image capture unit 154,based on information received, such as expected position of the featureand movement rate of the substrate, from the controller 132.

The LED light source is electrically coupled to a power supplyconfigured to provide voltage to the LED light source that results in adesired luminosity for imaging in the durations described above. Anumber of LED emitters in the LED light source may be selected toprovide total lumens for capturing a clear image in the short durationsdescribed above. In one example, the LED array may be an array of 24LEDs having emissions at 610-650 nm, each LED having luminous output ofabout 65 lumens at an applied voltage of about 1.8 V. LEDs that may beused include the LUXEON® Star LXZ1-PHO1 LEDs available from Lumileds, ofSan Jose, Calif. In one case, 40 such LEDs are assembled into a 5×8array. In another case, 24 such LEDs are assembled into a 4×6 array. Inother cases, 40 LEDs can be assembled into a circular profile. In stillother cases, more LEDs can be used. For example, in one case, 50 LEDscan be used for a light source.

FIG. 2 is an elevation view of a position acquisition system 200according to one embodiment. The position acquisition system 200comprises the imaging system 150, with a substrate 202 disposed on thesubstrate support 102 for processing. The imaging system 150 isoperatively coupled to the imaging controller 158, which is furtheroperatively coupled to the system controller 132, as described above.The imaging system 150 may also be operatively coupled to a positioningcontroller 204 that can control and adjust the position of the imagingsystem 150. The positioning controller 204 may adjust the position ofthe imaging system 150 with respect to the dispensers of the dispenserhousing 119 of FIG. 1.

In this case, the imaging system 150 includes a LED light source 206 andan imaging unit 208. An optical assembly 210 optically couples the LEDlight source 206 and the imaging unit 208 to the substrate 202 forimaging. The optical assembly may include one or more lenses, prisms,fibers and/or mirrors for directing and/or focusing light reflected fromthe substrate into the imaging unit 208. An optical fiber 212 translatesthe radiation emitted by the LED light source 206 to an emission point214, which may be at an end of the optical assembly 210 distal to thesubstrate support 102, may extend beyond the end of the optical assembly210 to a location closer to the substrate support 102 than the end ofthe optical assembly 210, or may be recessed within the optical assembly210. The optical fiber 212 is supported by a support 216 that maintainsa position of the emission point 214. Radiation is emitted from theoptical fiber 212 at the emission point 214 and traverses a gap betweenthe emission point 214 and the substrate 202 to provide an illuminationfield 218. Dimension of the illumination field 218 can be controlled bycontrolling location of the emission point 214 with respect to thesubstrate 202. During processing, the substrate is typically scannedwith respect to the imaging system 150 to illuminate portions of thesubstrate to be imaged, as indicated schematically by the arrow 220. TheLED light source 206 is activated at times when the portion of thesubstrate to be imaged is partially or completely within theillumination field 218 as the relative scanning is performed, anddeactivated when the portion to be imaged has traversed the illuminationfield 218 for a time sufficient to capture the desired image of theentire area to be imaged. This may be when a first portion of the areato be imaged exits the illumination field 218, or when a last portion ofthe area to be imaged exits the illumination field 218. The LED lightsource 206 can be activated by closing a switch electrically coupledbetween a power source (not shown) and the LED light source 206. Theswitch may be controlled by signals sent from the controller 123(FIG. 1) or by a local controller for the LED light source 206, or acombination thereof.

FIG. 3 is an algorithm diagram of an image capture control algorithm 300according to one embodiment. The image capture control algorithm 300 isused with deposition devices such as the device 100. The image capturecontrol algorithm 300 creates triggers for initiating image capture of afeature on a substrate 301 by an image capture unit and for initiatingillumination by an illumination unit. The illumination unit is capableof generating short pulses of uniform radiation within an illuminationfield. The duration of the pulses is around 1 μsec, or shorter, toenable capturing images of a small feature on a substrate at relativerates of motion of up to 1 m/sec. An LED light source, for example anarray of LED sources having emission wavelength matched to a spectralsensitivity of the image capture unit and luminous output sufficient toenable capture of clear images during the short exposure durationsdescribed above, can be used.

The algorithm 300 uses a position markers, along with position signalsfrom the substrate holder to determine when to begin image capture bythe image capture unit and when to begin illumination by theillumination source. Generally the algorithm uses a defined coordinatesystem that is used by the controller to perform the algorithm 300. Thesubstrate has a defined origin point 302, which is positioned at a knownposition (x_(S), y_(S)) relative to a home position 304 of the holder(x_(H), y_(H)), which is also known. A design location 306 of a featureon the substrate (x_(F), y_(F)) is known relative to the origin point302 of the substrate. In an embodiment where the substrate is moved inthe y-direction during processing, the y-position of the holder,substrate origin, and feature are y_(h), y_(s), and y_(f), respectively.These are offset from their various home positions in the y-direction byan identical distance 308. If the imaging system is moved duringprocessing, the position of the illumination field 310 at any time isy_(i). The feature has design dimension of Δx_(F) and Δy_(F). Theillumination field 310 produced by the imaging system has a knownlocation (x_(I), y_(I)) relative to the holder home position. Theillumination field also has dimensions Δx_(I) and Δy_(I). Thus, in they-direction, the illumination field extends from y_(I)−½Δy_(I) toy_(I)+½Δ_(I), or if the imaging system is moved, y_(i)−½Δy₁ toy_(i)+½Δy_(I). At any time during a process, the holder y-position y_(h)is known from actuator position.

The various position markers are provided to a controller, such as thecontroller 132. The algorithm determines when to activate the imagecapture unit and the illumination source to capture an image of thefeature, based on the expected location of the feature. The size of theillumination field is set to provide sufficient coverage that any offsetbetween the expected position of the feature and the actual position ofthe feature is less than an amount that keeps the entirety of thefeature in the illumination field during the exposure.

Let relative movement velocity of the substrate and the imaging systemin the y-direction be v, and let pulse duration be t. The algorithmcomputes a light-on event to illuminate the feature 306. The light-onevent may be computed when the entire feature 306 is within theillumination field 310. This occurs when, in the y-direction,y_(f)−½Δ_(F)=y_(i)−½Δy_(I). If the holder position is offset in they-direction relative to the substrate origin by y_(HS) then the holderposition at light-on time is y_(i)−½Δy_(I)−y_(f)+½Δy_(F)+y_(S)+y_(HS).The light-on event can be computed in terms of holder position, time, orany other parameter that can be determined from the parameters of thedeposition job. If the light-on event is rendered as a time, it will bethe time at which vt=y_(i)−½Δy_(I)−y_(f)+½Δy_(F).

The duration light is on is minimized to avoid distortion of the image.The substrate and the imaging system may be relatively moving when theimage is captured. Illuminating the scene longer than necessary tocapture the desired image could result in reduction in the clarity ofthe image. The algorithm computes a light-off event when, after thelight-on event, the feature has traversed the illumination field. Thisoccurs when, in the y-direction, y_(f)+½Δy_(F)=y_(i)+½Δy_(I). Thealgorithm 300 can compute light-off holder position asy_(i)+½Δy_(I)−y_(f)−½Δy_(F)+y_(S)+y_(HS) or the time at which vt=y_(i)+½Δy_(I)−y_(f)−½Δy_(F). The duration of the pulse is selected to be thetime for the feature to transit the illumination field, which is

$t = {\frac{1}{v}{\left( {{\Delta\; y_{I}} - {\Delta\; y_{F}}} \right).}}$

The imaging system is positioned such that the x-position of theillumination field is the same as the designed x-position of thefeature. The imaging system uses illumination sources that cantransition from zero to peak intensity, and from peak intensity to zero,in a time much less than the pulse duration. LED light sources can betransitioned as quickly as electric potential across each LED lightsource can be transitioned, so LED light sources can be pulsed in theshort durations described herein. LED light sources also emit uniformradiation that, in most cases, does not need further uniformizing toenable clear images.

FIG. 4 is a flow diagram summarizing a method 400 of capturing an imageof a position feature on a substrate. At 402, a substrate is positionedon a substrate support of a processing apparatus. Typically theprocessing apparatus is used to perform a process, such as materialaddition to, or removal from, the substrate, and positioning features ofthe substrate are used to guide the process. The position feature may bea special feature, such as a mark or structure, added to the substratespecifically for positioning the substrate, or the position feature maybe a feature added to the substrate for some other purpose and used herefor positioning the substrate.

At 404, the substrate is positioned to be photographed by an imagingsystem. The substrate can be moved into position with respect to theimaging system by applying a substrate holder to move the substrate. Insome cases, the substrate support includes a frictionless surface suchthat the substrate holder can move the substrate with little resistance.The imaging system can also be moved in some cases. For example, theimaging system may be deployed on a positioning system using an airbearing coupled to a rail. The imaging system may include an LED lightsource oriented to direct illuminating radiation toward an imaging area.An imaging unit is positioned proximate to the LED light source to imageradiation reflected from the substrate.

The substrate is positioned for imaging at a location determined by anexpected location of the positioning feature. The expected location ofthe positioning feature is a pre-determined location on the substratewhere the positioning feature is expected to be found. The imagingsystem and the substrate are mutually positioned such that the expectedlocation is near an illumination field of the illumination source.

At 406, the substrate is scanned with respect to the imaging system. Theexpected location of the positioning feature is moved toward an edge ofthe illumination field of the illumination source. When the expectedlocation is at a pre-determined distance from the edge of theillumination field, the imaging unit is activated to begin acquiringimage data. At this time, the illumination source is not active.Typically, the processing apparatus has an enclosure that isolates thesubstrate support and imaging system, so any light source other than theillumination source is minimal.

At 408, the illumination source is activated when an image of thepositioning feature can be captured by the imaging unit. Theillumination source may be activated when a portion of the positioningfeature is expected to enter the illumination zone, when a fraction ofthe positioning feature inside the illumination field of theillumination source is expected to be at a maximum, or when the entirepositioning feature is initially expected to be within the illuminationfield of the illumination source. In one case, the illumination sourceis activated when a leading edge of the positioning feature is expectedto reach an edge of the illumination field. The expected position of thepositioning feature may be at an extremity of the positioning feature,or at a center of the positioning feature. If the expected position ofthe positioning feature is at an extremity thereof, the illuminationsource can be activated when the expected position of the positioningfeature is expected to reach the edge of the illumination field. If theexpected position of the positioning feature is at a center thereof, aknown dimension of the positioning feature can be used to determine anexpected position of an extremity of the positioning feature, and theillumination source can be activated when the expected position of theextremity of the positioning feature is expected to reach the edge ofthe illumination zone.

In other cases, the illumination source can be activated when thepositioning feature, or a large portion thereof, is expected to beentirely within the illumination field of the illumination source. Inthis case, the illumination source is activated when a trailing edge ofthe positioning feature is expected to reach the edge of theillumination zone, as determined by the known geometry and expectedlocation of the positioning feature. Waiting until a maximum portion, orall, of the positioning feature is within the illumination field of theillumination source to activate the illumination source minimizesexposure time for capturing the image, and therefore minimizes movementof the substrate during image capture. Minimizing movement of thesubstrate during image capture results in the sharpest image.

At 410, the substrate and imaging system are mutually scanned such thatthe positioning feature, or a portion thereof, transits the illuminationfield of the illumination source during a transit time. The transit timemay be defined in a number of ways. In one case, the transit time is atime between when a first extremity of the positioning feature entersthe illumination field of the illumination source and the last extremityof the positioning feature exits the illumination field of theillumination source. In another case, the transit time is a time betweenwhen a last extremity of the positioning feature enters the illuminationfield, wherein the positioning feature has no other extremities thatenter the illumination field thereafter, and a time when a firstextremity of the positioning feature exits the illumination field. Ineither case, all or only a portion of the positioning feature maytransit through the illumination field. The time during which thetransit takes place may be as little as 1 μsec. The transit time can bedetermined using a known dimension of the illumination field and by thevelocity of transit.

At 412, the illumination source is deactivated. An active time of theillumination source is defined as the time between when the illuminationsource is activated and when the illumination source is deactivated. Theactive time of the illumination source may be the same as the transittime, or different. The active time of the illumination source may becoincident and simultaneous with the transit time, may overlap with thetransit time, or may encompass the transit time. In one case, the activetime is coincident and overlapping with the transit time. In anothercase, the active time is coterminous and overlapping with the transittime. In yet another case, the active time is concurrent with thetransit time, and can overlap with the transit time or encompass thetransit time. In any event the active time and transit time are relatedto illuminate a desired portion of the positioning feature during thetransit time.

In the event an image of the entire positioning feature is desired, butcannot be captured in a single exposure, due for example to the size ofeither the illumination field of the illumination source or the size ofthe imaging field of the imaging unit, the substrate and imaging systemcan be repositioned for a second exposure to capture an additionalportion of the positioning feature in a manner similar to the method400.

At 414, the imaging unit is deactivated. An imaging time can be definedas the time between when the imaging unit is activated and when theimaging unit is deactivated. The imaging time is longer than the activetime of the illumination source, since obtaining short light pulses ismore straightforward than obtaining useful exposures with short exposuretimes. In the embodiments described herein, the positioning features mayhave dimension on the order of 1 μm, and scan velocity of the substratemay be as much as 1 m/sec. Thus, in some cases images are captured in aduration of 1 μsec using the methods and apparatus described herein.Such short duration exposures are more readily accomplished using ashort active time of 1 μsec with a longer imaging time of 1 msec ormore.

The method 400 may be repeated to image a plurality of positioningfeatures. In each case, an expected position of the positioning featureis known, and the substrate and imaging system are positioned to placethe expected position near the illumination field of the illuminationsource. It should be noted that, due to errors in placement of thesubstrate, errors in placement of the imaging system, errors inapplication of the positioning features to the substrate, and thermaldisplacements and distortions, an image taken using the expectedlocation of the positioning feature may not capture the desired image.In such cases, the captured image can be analyzed to determine magnitudeand direction of a position correction that can be applied. The method400 can then be repeated, applying the position correction before orduring performance of the method 400. Typically the expected position ofthe positioning feature is modified by the position correction prior torepeating the method 400, but a bias can also be applied to the positionof the substrate and/or the imaging system in addition to, or insteadof, modifying the expected position of the positioning feature.

FIG. 5 is a flow diagram summarizing a method 500 that can be used withthe apparatus and other methods described herein. The method 500 is amethod of determining position and orientation of a positioning featureof a substrate from a pulse-illuminated image. At 502, an image of anarea of a substrate is obtained at a location where a positioningfeature is expected to be found. The image is obtained using the imagingsystem described herein.

At 504, a set of grid points is defined within the image. The gridpoints are defined by x-y coordinates in a common coordinate system withpoints in the image. That is, the image is taken by locating the imagingsystem at a point defined by coordinates. The geometry of the imagingsystem determines the coordinates of the boundaries of the image in thecoordinate system. The grid points are defined between the coordinatesof the boundaries of the image. Any number of grid points may be used,with more grid points being helpful when the positioning feature has amore complex shape.

The expected shape and size of the positioning feature is typically alsodefined by coordinates in the same coordinate system. For example,vertices of a polygonal positioning feature can be defined by an orderedset of coordinate pairs, where adjacent coordinate pairs define thelocations of vertices connected by edges. For non-polygonal shapeshaving curved contours, the coordinates may define adjacent points onedge contours of the shape. More points in the shape definition of sucha shape improve the shape definition by minimizing the error of assumedstraight edges between neighboring points.

At 506, for each grid point defined at 504, a plurality of lines isdefined through the grid point. The lines can be defined as a set ofcoordinate pairs representing each pixel of the image along the lines,or the lines can be defined as a set of end points. The number of linesis pre-determined based on the complexity of the shape being imaged, andmay be increased if a first performance of the method 500 yieldsunsatisfactory definition of the positioning feature in the image. Thelines are generally selected to cover a plane uniformly, for exampleradiating at equal angles from the origin point.

At 508, for each line defined at 506, a brightness change from pixel topixel of the image along the line is determined. For each pixel P¹ onthe line, defined by a coordinate pair (x_(p) ₁ , y_(p) ₁ ) belonging tothe set of coordinate pairs defining the line, the brightness of thepixel B_(p) ₁ is ascertained. The brightness B_(p) ₂ of at least oneneighboring pixel P² on the line, at coordinates (x_(p) ₂ , y_(p) ₂ ) isalso ascertained. The two brightnesses are subtracted, B_(p) ₂ −B_(p) ₁to determine brightness change at pixel P¹. Absolute value is typicallyused. This type of brightness change is “forward” brightness change.Alternately, “backward” brightness change, where P¹ is compared to thepreceding pixel P⁰, or “central” brightness change, where averagebrightness change from P⁰ to P¹ to P², can be used.

Brightness change is generally used to indicate where a boundary may belocated in the image. At 510, a pre-determined number of the highestbrightness change pixels, points along the line having the highestmagnitudes of brightness change, are recorded as candidates for a shapeboundary within the image. Operations 506, defining lines, 508,analyzing brightness changes along the lines, and 510, recording thelargest magnitude brightness changes, are repeated for all grid pointsdefined for the image. From this process, a set of points is acquiredrepresenting candidate points for defining the edge of the shapecaptured in the image.

At 512, the recorded points are analyzed to determine which points lieon the boundary of the image of the positioning feature. Any number ofshape recognition algorithms can be used to determine which points canbe used to define the location of the boundary edge of the shape in theimage. Selection of the algorithm can be influenced by the known shapeof the positioning feature. For example, if the shape is known to becircular, or nearly so, equality of distance from a point can be used asa search criteria. For more complex shapes, distance based signaturescan be computed in a matching algorithm. For example, test shapesbounded by the known shape and dimension of the positioning feature canbe defined by coordinates, and distances of the recorded points from thetest shape can be determined. The test shape can then be sought, withinthe constraints of the known shape and dimension, which minimizes thedistance statistic. The result of such search can be improved byexcluding statistical outliers to resolve a “best” score for each testshape, and the test shape with the best overall score can be identifiedas the likeliest representation of the shape in the image.

From such a best test shape, further refinement of the shape can beperformed. For example, if the test shape has boundaries defined bycoordinate pairs of pixels on the boundary, curvature metrics can beapplied pixel by pixel to improve the test shape fit to the recordedpoints. At 514, a set of coordinates is defined as representing aboundary of the positioning feature in the image based on the analysisof 512.

After the boundary of the positioning feature in the image is defined incoordinates, characteristics of the positioning feature in the image canbe determined. At 516, a centroid of the coordinates defining theboundary of the positioning feature can be computed as the “center” ofthe feature. This location can be recorded in the system as the actuallocation of the positioning feature on the substrate. Alternately, amaximum or minimum x-value and a maximum or minimum y-value can be usedas the location of the positioning feature. When the position is definedat 516, a position error of the positioning feature can be determined at518. The position error is the difference between the coordinates of thepositioning feature as defined from the image analysis and the expectedcoordinates of the positioning feature. This position error can be usedto adjust processing plans for the substrate.

At 520, a rotation error can be defined for the positioning feature. Arotation transformation can be applied to the coordinate set definingthe boundary of the positioning feature in the image. For example, arotation angle can be defined in radians, and an x-y shift of each pixelin the coordinate set defining the boundary of the positioning featurein the image can be defined based on radial coordinates of each pixel.After applying the rotation transformation, a difference between therotated coordinate set of the image boundary and the expected coordinateset of the positioning feature boundary can be computed. The degree ofrotation that minimizes the difference can be used as the rotation errorof the image. The rotation error may be computed before or afteradjusting for any position error identified at 518.

At 522, a mis-shape error can be defined for the positioning feature.The mis-shape error documents distortion of the positioning feature fromits expected shape. The mis-shape error, if not detected andcompensated, can drive processing errors introduced based on theassumption that the positioning feature is shaped properly. For example,if one corner of a square positioning feature is misplaced, such thatthe positioning feature is not quite square, the positioning feature maybe found and located, but it's location may be mis-recorded for theprocessing system based on the mis-shape. The mis-shape error istypically determined after compensating for any position error androtation error. A pixel-by-pixel error of the position- androtation-compensated image can be computed and recorded as the mis-shapeerror. The recorded location of the positioning feature, for purposes ofprocessing the substrate, can be adjusted based on the identifiedmis-shape error.

The method 500 can be used to locate and define a plurality ofpositioning features of a substrate. Errors detected in a plurality ofpositioning features can be analyzed to identify systematic errors inplacement and orientation of a substrate in the processing system. Forexample, similar rotation or position errors among a plurality ofpositioning features can indicate an overall rotation or position errorin placement of the substrate. Different rotation or position errors canindicate distortion of a substrate, or misplacement of positioningfeatures on the substrate. The method 500, and variations thereof, areperformed using a digital processing system programmed with instructionsappropriate to render the various coordinates and calculations referredto in the method 500. The digital processing system accepts datarepresenting the image from the imaging unit, and automaticallyidentifies the boundaries of the feature in the image, and optionallythe position error, the rotation error and the mis-shape error of thepositioning feature in the image. The results of the method 500 can beused to control precision deposition of material onto a substrate using,for example, the deposition apparatus 100 of FIG. 1.

FIG. 6 is an isometric top view of a deposition device according toanother embodiment. The device of FIG. 6 is similar to the device ofFIG. 1, with the difference that the imaging system 150 is absent.Instead, a first imaging system 650 is movably coupled to an imagingrail 604, which is part of a deposition assembly support 616. Thedeposition assembly support 616 is like the deposition assembly support116 of FIG. 1, including the beam or rail 117, which is a depositionrail in this case. The deposition assembly support 616 include anextension 620 that supports a first imaging system 650 and a secondimaging system 652. The extension 620 comprises a first riser 622 thatextends from a first end 624 of the beam 117 and a second riser 626 thatextends from a second end 628 of the beam 117 opposite from the firstend 624. The extension 620 further comprises the imaging rail 604, whichextends from the first riser 622 to the second riser 626, substantiallyparallel to the beam 117.

Each of the first imaging system 650 and the second imaging system 652is substantially the same as the imaging system 150. The first imagingsystem 650 is coupled to the imaging rail 604 by a first imagingcarriage 654. The second imaging system 652 is coupled to the imagingrail 604 by a second imaging carriage 656. The dispenser housing 119 isbetween the first imaging system 650 and the second imaging system 652.Each of the first imaging carriage 654 and the second imaging carriage656 has a lateral extension that supports the first and second imagingsystems 650 and 652 at a clearance from the imaging rail 604. Theclearance allows each of the first and second imaging systems 650 and652 to move along substantially the entire length of the imaging rail604, with no interference from the deposition housing 119.

The device 600 has four independently movable imaging systems. The twoimaging systems 650 and 652 described above are located on a first sideof the deposition support assembly 616. The device 600 has a thirdimaging system 660 and a fourth imaging system 662, each of which is animaging system like the imaging systems 650 and 652. Here, the imagingrail 604 is a first imaging rail, and a second imaging rail 664 is partof the deposition support assembly 616. The first and second imagingrails 604 and 664, in this case, are both disposed on the two risers 622and 626, and extend parallel, each to the other, between the two risers622 and 626. The imaging systems 660 and 662 are each supported on thesecond imaging rail 664 by an imaging carriage. Specifically, a thirdimaging carriage 674 couples with the second imaging rail 664 to supportthe third imaging system 660, and a fourth imaging carriage 676 coupleswith the second imaging rail 664 to support the fourth imaging system662. A space between the imaging rails 604 and 664 allows the first andsecond carriages 654 and 656 to move along the first imaging rail 604without interference from the third and fourth carriages 674 and 676. Inthis way, all four imaging systems can be positioned along substantiallythe entire length of the deposition support assembly 616. Use ofmultiple imaging systems allows for a high volume of images to becaptured in a smaller time, thus speeding up processes that depend onsuch imaging.

Any number of the imaging systems described herein can be used with sucha device. In FIG. 6, four imaging systems are illustrated, but anynumber of such imaging systems can be used. For example, two imagingsystems can be used on one of the two imaging rails, or two imagingsystems can be used, one on each imaging rail. Imaging systems can beadded to one or both imaging rails by merely placing the carriage of animaging system on the desired imaging rail. In some cases, the carriagescouple to the imaging rails using air bearings, so the air bearing ofthe added imaging system can be activated to allow the added imagingsystem to move along the chosen imaging rail. Deploying a plurality ofimaging systems that use LED light sources allows a device to use thebrightness, uniformity, and fast pulse time of LED radiation to image aplurality of locations simultaneously, thus increasing the speed ofimaging various portions of a substrate. Using multiple imaging devicescan also increase precision of imaging at a single location on thesubstrate if two or more images of the location are acquired andcompared.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the present disclosure may be devisedwithout departing from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

What is claimed is:
 1. A deposition device, comprising: a substratesupport; and a deposition assembly comprising an imaging system disposedacross the substrate support, the imaging system comprising an LED lightsource.
 2. The deposition device of claim 1, wherein the depositionassembly comprises a rail attached to a support located on oppositesides of the substrate support, and a dispenser assembly movably coupledto the rail.
 3. The deposition device of claim 2, wherein the dispenserassembly houses the imaging system.
 4. The deposition device of claim 1,wherein the imaging system comprises an array of LEDs having an emissionwavelength of at least about 600 nm.
 5. The deposition device of claim4, wherein the imaging system further comprises an imaging unit having asensitivity profile matched to the emission wavelength of the LEDs. 6.The deposition device of claim 5, wherein the LED light source has apulse duration of 1 μsec or less.
 7. The deposition device of claim 6,further comprising a controller configured to scan a substratepositioned on the substrate support relative to the imaging system,activate the imaging unit for an imaging time, and activate the LEDlight source for an active time, wherein the active time is encompassedby the imaging time.
 8. The deposition device of claim 7, wherein theLED light source is coupled to a fiber waveguide.
 9. The depositiondevice of claim 1, wherein the imaging system is one imaging systemamong a plurality of imaging systems coupled to the deposition assembly,each imaging system of the plurality of imaging systems comprising anLED light source.
 10. A method of imaging a feature on a substrate,comprising: scanning the substrate relative to an imaging systemcomprising an LED light source and an imaging unit; activating theimaging unit before an extremity of the feature reaches an illuminationfield of the LED light source; activating the LED light source when aportion of the feature reaches the illumination field; deactivating theLED light source after an active time; and deactivating the imaging unitafter an imaging time, wherein the imaging time encompasses the activetime.
 11. The method of claim 10, wherein the active time is less than 5μsec.
 12. The method of claim 11, wherein the imaging unit is a camerahaving sensitivity matched to the emission wavelength of the LED lightsource.
 13. The method of claim 12, further comprising relativelypositioning the substrate and the imaging system based on an expectedlocation of the feature.
 14. The method of claim 13, further comprisingautomatically identifying a boundary of the feature in the image. 15.The method of claim 14, further comprising automatically identifying aposition error of the feature.
 16. The method of claim 14, furthercomprising automatically identifying a rotation error of the feature.17. The method of claim 10, wherein the imaging system is a firstimaging system, and further comprising: capturing a first image of thefeature using the first imaging system; and capturing a second image ofthe feature using a second imaging system, the second imaging systemcomprising an LED light source.
 18. The method of claim 17, wherein thefirst imaging system and the second imaging system are coupled to asupport extending across a substrate support on which the substrate isdisposed for imaging.
 19. A deposition device, comprising: a substratesupport; and a deposition assembly comprising an imaging system disposedacross the substrate support, the imaging system comprising: an LEDlight source fiber coupled to an optical assembly to direct radiationfrom the LED light source toward the substrate support; and an imagingunit disposed to capture radiation reflected through the opticalassembly.
 20. The deposition device of claim 19, further comprising aposition controller to position the imaging system.